JP2962367B2 - Refrigerator with thawing room - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerator with a thawing room for thawing frozen food.

[0002]

2. Description of the Related Art Heretofore, there has been known an example in which a heater is used for thawing frozen food. For example,
An example is disclosed in Japanese Patent No. 25414, which will be described below with reference to FIGS.

Reference numeral 1 denotes a thawing box, which is formed of a metal or synthetic resin or the like in a box shape, and an inner box 2 made of aluminum or the like having good thermal conductivity provided at an appropriate interval inside the outer box 2. It is composed of a metal inner box 3. Reference numeral 4 denotes a linear heater, which is thermally conductively adhered to the inner box 3 by an aluminum box 5 so that the bottom surface of the thawing box 1 is sparse and the top surface is dense. 6 is the outer box 2 and aluminum foil 5
It is a heat insulator interposed between them.

In this configuration, when the food 7 to be thawed is placed on the bottom surface of the defrosting box 1 and the thawing operation is started, heat is applied from the entire circumference of the inner box 3 by the heating of the heater 4, and the food 7 to be thawed is heated. Is characterized by being heated and thawed.

[0005]

However, in such a configuration, heat is transmitted from the bottom of the thawing box 1 to the bottom of the food 7 to be thawed by heat conduction, so that the thawing of the bottom is possible. The effect of the radiant heat from the upper surface and the side surface of the box 1 to the food 7 to be thawed is almost non-existent because the heat ray wavelength from the heater 4 through the inner box 3 is in the near-infrared region of 5 μm or less. Heating is performed by heat transfer by convection of the heated air in 1.

[0006] For this reason, the thawing unevenness between the central part and the surface part of the food 7 to be thawed tends to be large and the thawing time is long, and the thawing quality depends on the size and weight of the food. There was a problem.

Further, if the food is left as it is after the thawing is completed, especially for living organisms such as fish meat, the deterioration due to the high ambient temperature occurs. There was also a problem that it could not be used with confidence.

An object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide a thawing room in which freezing unevenness is small, and thawing can be performed in a short time and with ease, especially in a refrigerator.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a refrigerator with a thawing room according to the present invention comprises a radiant heater on the upper surface of the thawing room, a reflecting plate for covering the upper part thereof in a curved shape, and a heater and a temperature sensor on the bottom surface. A thawing plate on which a food to be thawed is placed is provided by providing a bottom plate in close contact. The reflection plate is provided with a discharge port for cool air, and a discharge pattern is formed on the back side thereof to communicate with a damper thermostat provided at the entrance of the thawing chamber for adjusting the amount of inflow of cool air. For the thawing operation, a thickness setting switch for inputting the thickness of the food to be thawed is provided. In such a configuration, the damper thermostat is forcibly opened during the thawing, the blower is forcibly operated, and both the radiation heater and the heating heater are energized from the start of the thawing until the temperature sensor rises to a predetermined temperature. This step is defined as a first step, and in the subsequent steps, the power supply to the heater is stopped, and the power supply to the radiation heater is set to a predetermined temperature by the setting input of the thickness setting switch and the temperature of the temperature sensor to a predetermined temperature. A memory device for storing empirically-based control rules for determining an optimal time of the second stage after ascending;
Fuzzy logic operation is performed based on a time until the temperature sensor rises to a predetermined temperature and a control rule extracted from the memory device, and fuzzy inference means for calculating the time of the second stage is provided. A control means is provided in which the rate is reduced stepwise so as to be intermittently energized, and at the time of non-thawing, the thawing chamber is maintained at a third temperature zone between the refrigeration temperature and the freezing temperature.

[0010]

According to the present invention, indirect radiation is performed through the top and side surfaces and the reflection surface of the food to be thawed by the above-described structure, and the heat is absorbed substantially evenly from the top and side surfaces of the food to be thawed, and at the same time, the bottom surface The heat transfer heating is also performed from the heater of the above, and the heat is absorbed. Until the temperature sensor on the bottom surface rises to a predetermined temperature, both heaters are energized, and the temperature of the food to be thawed rapidly rises. Next, the time from the start of thawing until the temperature sensor rises to a predetermined temperature, that is, the time of the first stage, is read.

Based on this time and the setting input of the thickness setting switch, the optimum value of the time of the second stage of the defrosted food is determined by performing a fuzzy logic operation from a control rule based on an empirical rule. The temperature gradually decreases, and cool air is supplied from a discharge port provided in the reflection plate via the damper thermostat, thereby suppressing a rise in the temperature of the food surface. After the thawing is completed, the food temperature is automatically maintained in the third temperature zone between refrigeration and freezing by the temperature control action of the damper thermostat to keep the food cool.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A refrigerator with a thawing compartment according to an embodiment of the present invention will be described below with reference to FIGS.

A refrigerator body 8 comprises an outer box 9, an inner box 10, and a heat insulating material 11 filled between the two boxes 9, 10. Reference numeral 12 denotes a cooling room (hereinafter referred to as a refrigeration room 12).
Reference numeral 13 denotes a freezer compartment formed above the refrigerating compartment 12. Reference numeral 14 denotes a thawing chamber provided in the lower part of the refrigerator compartment 12.

Reference numeral 15 denotes a refrigerating cycle compressor provided at the bottom of the refrigerator main body 8, and reference numeral 16 denotes a cooler housed in the back of the freezing compartment 13. Reference numeral 17 denotes a blower for forcing the cool air cooled by the cooler 16 into the refrigerating compartment 12, freezing compartment 13, and thawing compartment 14, and 18 is provided at the inlet of the thawing compartment 14 to supply cold air by an electric input. This is a damper thermometer for adjusting the amount, and the damper 20
Is configured to open and close.

Reference numeral 21 denotes a discharge duct for guiding cool air from the blower 17 to the thawing chamber 14, and reference numeral 22 denotes a suction duct for returning the cool air that has cooled the inside of the thawing chamber 14 to the cooler 16.

Next, the detailed structure of the thawing chamber 14 will be described. Reference numeral 23 denotes an outer box made of a synthetic resin, and 24 denotes an inner box made of a metal such as aluminum, which has a curved reflecting plate 25, a bottom plate 26 disposed below the reflecting plate 25, and both plates 2.
5, 26 are formed by substantially U-shaped side plates 27 connected to three sides.

A door 28 is provided at the front opening of the inner box 24 so as to be openable and closable. The door 28 has a double structure made of a synthetic resin in which an air layer is formed to enhance heat insulation. Reference numeral 29 denotes a quartz glass tube radiation heater provided at a predetermined interval facing the reflection plate 25 of the inner box 24, and radiates far infrared rays of about 5 μm or more. It is also possible to increase the radiation efficiency of far-infrared rays by baking and painting a ceramic paint mainly composed of such a material.

Reference numeral 30 denotes a protective net for preventing burns, which is attached to cover the radiant heater 29 at regular intervals. Reference numeral 31 denotes a linear heater that is thermally conductively adhered to the back surface of the bottom plate 26 with an aluminum foil or the like, and 32 is a thermistor or the like that is thermally conductively adhered near the center of the back surface of the bottom plate 26. It is a temperature sensor. 33 is the bottom plate 2
6 is a thawing tray that is detachably mounted on the tray 6 and includes a metal dish 35 such as aluminum on which the food 34 to be thawed is placed, and a synthetic resin frame 36 surrounding the outer periphery.

Reference numeral 37 denotes a heat insulating material inserted between the outer case 23 and the inner case 24. The upper portion communicates with the discharge duct 38 communicating with the discharge duct 21 and the damper thermometer 18, and the rear portion communicates with the suction duct 22. A suction air passage 39 is formed.
Reference numeral 40 denotes a plurality of discharge ports formed in the reflection plate 25 of the inner box 24 so as to communicate the inside of the thawing chamber 14 with the discharge air path 38.
Reference numeral 1 denotes a suction port formed in the side plate 27 of the inner box 24 so as to communicate the inside of the thawing chamber 14 with the suction air passage 39.

Reference numeral 42 denotes an operation plate provided on a part of the outer shell of the refrigerator main body 8, and has three thicknesses (for example, "thin"... 15 mm or less, "normal"... 15-30 mm, Thickness setting switch 4 to select “thick” ... 30 mm or more)
3, and a thawing switch 44 for starting or stopping the thawing action.

Next, the control relationship will be described. Reference numeral 45 denotes control means (hereinafter referred to as a microcomputer 45) comprising a microcomputer or the like, a timer 46 for counting the time of the first stage of the decompression control composed of three stages, a timer 47 for counting the time of the second stage, A timer 48 for counting the time of the third stage,
And, for example, the intermittent duty ratio X% (ON... X ₁ sec, OFF
...... x ₂ sec) timer 49 for setting the intermittent energization ratio Y%
(ON... Y ₁ sec, OFF... Y ₂ sec).

An input terminal of the microcomputer 45 is provided with a freezing room temperature detecting means 51 for detecting the temperature in the freezing room for controlling the operation of the compressor 15 and the blower 17, and a food provided with the temperature sensor 32. A temperature detecting means 52, a defrosting chamber temperature detecting means 53 composed of the same temperature sensor 32, the thickness setting switch 43, and a defrosting switch 44;
Is connected to the output terminal, the compressor 15 and the blower 1
7, damper thermo 18, radiation heater 29, heater 3
Drive means 54, 5 such as electromagnetic relays for driving
5, 56, 57 and 58 are connected.

Further, the microcomputer has a fuzzy inference unit 54 for determining the second stage time 55 by using the first stage time as an input.

In such a configuration, the block diagram of FIG.
The operation will be described based on the flowchart of FIG. 6, the fuzzy rule of FIG. 7, and the time chart of FIG.

First, the food to be thawed (eg, beef steak meat having a thickness of 20 mm) 34 is placed almost at the center of the thawing dish 33 and placed on the bottom plate 26. First, in STEP 1, the thickness of the food 34 to be thawed is set to three types of “thin”, “normal”, and “thick” using the thickness setting key 43 (for example, “normal” is set in this case). Do).

Next, in STEP 2, the decompression switch 4
By turning on 4, the thawing action is started. When the defrosting control starts, the timer 46 of the first stage starts counting time in STEP3.
In 4, the radiation heater 29 (for example, 100 W) and the heater 31 (for example, 10 W) are continuously energized to forcibly operate the blower 17 and forcibly open the damper 20 of the damper thermo 18.

For this reason, far-infrared rays of 5 μm or more are mainly radiated from the upper surface to the upper side of the food 34 to be thawed continuously or directly or indirectly via the reflection plate 25. In general foods having an absorption wavelength band in the wavelength range, far infrared rays are efficiently absorbed, and the food to be thawed 3
The heat quickly penetrates into the relatively inside of No.4. In addition, the bottom surface of the food 34 to be thawed, which cannot be sufficiently heated by the radiation heater 29,
In addition to the continuous heat transfer heating from the first stage, the temperature of the food 34 to be thawed in the thawed state (for example, −20 ° C.) can be quickly increased in the first stage.

On the other hand, the cool air cooled by the cooler 16 is guided to the discharge air passage 38 in the thawing chamber 14 through the discharge duct 21 and the damper thermostat 18 in the refrigerator main body by the forced air blowing action of the blower 17, and Is blown down in a shower form from a large number of discharge ports 40 of the above. For this reason, the above-described radiation heater 2
9 together with the effect of the penetration of heat into the food by the far-infrared radiation, the food to be thawed 34 while keeping the surface temperature from rising.
The thawing proceeds in a state where the temperature unevenness between the surface and the center does not increase.

The air warmed by the heating action in the thawing chamber 14 is returned to the cooler 16 through the suction duct 41 of the refrigerator body 8 from the suction port 41 and the suction air passage 40 provided at the rear part of the room, and again. It cools and repeats its circulation. While the continuous heating action with such cooling action proceeds, STE
At P5, the temperature T of the temperature sensor 32 is set to a set value T '(for example, 2
0 ° C) higher or lower, and if lower, STEP5
Wait until it gets high. In STEP5, the temperature is high (T
≧ 20 ° C.), it is diagnosed that the first stage has been completed, and the routine proceeds to STEP 6 where the timer 46 of the first stage is terminated.
Stops time counting and takes time t from the start of thawing.
₁ (for example, 6 minutes ) is stored in the microcomputer 45 as the time of the first stage.

Here, the required time t ₁ is for judging whether or not the food is easy to thaw, and depends on the weight, components and shape of the food. The required time t ₁ is determined by the fuzzy inference means 54.
Is input to. The memory device 56 is a fuzzy inference means 5
4 stores control rules necessary for fuzzy inference. Fuzzy inference for obtaining the second stage time following the first stage is executed based on the following control rules.

The control rules employed in this embodiment are as follows:
Rules. For example, rule R1: if the first stage time t ₁ is considerably short with a thin setting, the second stage time magnification is 1.1
To Rule R2: If the first stage time t ₁ is slightly shorter in a thin setting, the second stage time magnification is 1.0
To

And so on. Here, the second stage time factor is ratio to the first stage time t ₁ of the second stage time, that is, the second stage time = first stage time × the second stage time factor.

[0033] The language rule is inventors have determined from the rule of thumb was obtained from a number of experimental data, a control rule in order to extract the food in optimum condition, time multiple of the second stage
The ratio is as shown in (Table 1) depending on the thickness setting and the first stage time.

Table 1 shows the first stage time t ₁ in the horizontal direction.
Divided into 5 stages (NB = fairly short, NS = slightly short, ZO = normal, PS = slightly long, PB = fairly long), and the thickness of the food in the vertical direction (thin, normal, thick)
And the first stage time t ₁ divided above
The first stage time t ₁ and the optimal second stage time magnification with respect to the thickness of the food are set at the position where the thickness and the thickness of the food intersect. According to (Table 1), the inventor of the present invention has confirmed that an optimum defrosting performance can be obtained when the second stage time magnification is controlled.

[0035]

[Table 1]

The language rules are stored in the memory device 56 of FIG. Next, the fuzzy inference means 54 takes out the control rules previously stored in the memory device 56, calculates the second stage time magnification by fuzzy inference, and sets the second stage time timer 47.

The rule of the control rule R1, rule R2,..., Rule R15 is the thickness of the food, the first stage time t.
_Since the second stage time magnification with respect to ₁ is determined stepwise, when fine control is performed, the degree to which the antecedent of the control rule is satisfied is calculated, and the degree corresponding to the degree is calculated. It is necessary to estimate the second stage time magnification. Therefore, in this embodiment, a member shop function of fuzzy variables is used to calculate the degree.

FIG. 7 shows the membership functions μNB (t ₁ ), μNS (t ₁ ), μZO of the fuzzy variables NB, NS, ZO, PS, PB with respect to the first stage time T ₁ .
(T ₁ ), μPS (t ₁ ), and μPB (t ₁ ).

The fuzzy inference executed by the fuzzy inference 54 is based on the control rule 1, rule 2,.
A fuzzy logic operation is performed using the membership function of No. 7 to calculate the second stage time magnification. The center of gravity method was used as the inference form. Next, the inference means will be described. The thickness of the food is set by the thickness setting switch 43 at the time of starting thawing. Also for the first stage time than membership function of Figure 7 to determine the degree of each stage (5-stage) in STEP7.

Next, in STEP 8, five stages, that is, N
B, NS, ZO, PS, and PB are represented by h (N
B), h (NS), h (ZO), h (PS), h (P
B), and the magnification of the second stage time for each stage is a (NB), a (NS), a (ZO), a (P
S), a (PB), and the optimal time magnification of the second stage is a ₀ ,

[0041]

(Equation 1) Becomes

Second stage time t ₂ = first stage time t ₁ × second stage time magnification a ₀ . This time is 5
5, the second stage time is set. Following this, the flow proceeds to STEP 9 and the second stage timer 47 is executed.
Starts time counting.

At the same time as counting the time of the timer 47, S
Proceeds to TEP10, intermittent energization rate X% of radiant heaters 29 Timer 51 = _{[x 1 sec / (x 1 +} x 2) sec ] × 100
(For example _{80% ...... x 1 = 60sec,} x 2 = 15sec)
Is intermittently energized. The power supply to the bottom heater 31 is stopped. At this time, the blower 17 and the damper 20 of the damper thermo 18 are continuously forcibly operated or forcibly opened to continuously introduce cool air.

As described above, in the second stage, the amount of heating is smaller than that in the first stage, and the intermittent heating is performed from the upper surface, so that the transfer of heat from the surface to the center of the food 34 to be thawed is promoted. At the same time, the thawing proceeds while suppressing the rise in the surface temperature by the cool air.

While the intermittent heating action including the cooling action proceeds, it is determined in STEP 11 whether or not the count time of the timer 47 has reached t ₂ (12 minutes ). Wait until you do. S
When the timer 47 counts t ₂ (12 minutes ) in TEP11, the second stage ends, and the flow proceeds to STEP12.

In STEP 12, the third stage timer 4
8 starts time counting. Setting time of the time the timer 48, i.e. the time t ₃ of the third stage has a thickness selected set at time t ₁ in STEP1 first stage separately predetermined constant b (e.g. in this case the thickness of "normal" b = 1)
T ₃ = b · t ₁ (1 × 6 = 6 minutes in this case)
Is automatically set to

At the same time as the timer 48 counts the time, the process proceeds to STEP 11, and the radiation heater 29 sets the intermittent duty ratio Y% of the timer 51 = [y ₁ sec / (y ₁ + y ₂ ) sec] × 100.
(For example if _{40% ...... y 1 = 20sec,} y 2 = 30sec)
Is intermittently energized. At this time, the power supply to the heater 31 on the bottom is stopped, and the blower 17 and the damper
Subsequently, the damper 20 of the motor 18 is forcibly operated or forcibly opened, and cool air is continuously introduced.

As described above, the third stage performs the heating operation with a smaller amount of heating than that of the second stage and with the cool air, and particularly, the bottom surface which is the heat transfer heating which easily raises the surface temperature. By not heating the heater 31 continuously, the rise in the temperature of the surface of the food 34 to be thawed is sufficiently suppressed, and as a result, the temperature difference between the central part and the surface part is small, and thawing with little uneven thawing can be realized.

While the thawing progresses in this way, STEP
At 14, it is determined whether or not the count time of the timer 48 has reached t ₃ (6 minutes ). 48 is t now in STEP14
_{When 3} (6 minutes) is counted, the third stage is completed and S
At TEP 15, the power supply to the radiation heater 29 is stopped, the forced operation of the blower 17 and the forced opening of the damper thermometer 18 are released, and the thawing is automatically terminated.

If the weight, components, and shape of the food 34 to be thawed change, the cooling heat capacity of the food changes, so that the temperature sensor 32
, The first stage time t ₁ changes.
In addition, the second stage time changes according to the length of the first stage time, and as a result, the thawing time automatically changes. Therefore, even if the weight, component, and shape of the food change, the product can be changed by fuzzy inference. Appropriate thawing is performed according to.

As described above, the thickness of the food 34 to be thawed is described as “normal”. However, in the case of “thick” and “thin”, a constant determined based on various experiments shown in the table is automatically selected. Then, thawing with less unevenness is performed with appropriate heating control. FIG. 9 shows a temperature characteristic and a time chart of the food 34 to be thawed during thawing.

[0052]

[Table 2]

The thawing time is also controlled by the internal penetration effect of far-infrared radiation and the heating control from the top and bottom during the initial stage of thawing.
It is possible to defrost for a relatively short time (for example, 20 to 25 mm for a beef steak meat having a weight of 200 g and a thickness of 20 mm). After the thawing is completed, the temperature of the thawing chamber 14 is controlled based on the temperature detected by the temperature sensor 32 as in the normal cooling.

Therefore, the food 34 to be thawed after thawing is about -3.
The temperature is immediately cooled so as to be stabilized at the partial freezing temperature of ° C, and the temperature does not further rise due to residual heat. Even after the thawing is completed, it is kept cool at a partial freezing temperature suitable for preserving living things such as fish and meat, so that the user monitors the ending of the thawing and immediately processes it as in the conventional case. Decompression can be done without any hassle. In addition, the food 34 to be thawed can be used at any time after the thawing is completed, which is extremely convenient.

[0055]

As described above, according to the refrigerator with a thawing room of the present invention, the following effects can be obtained.

(1) Radiant heating mainly using far-infrared rays from the upper surface by the radiant heater, heat conduction heating by the heater from the bottom surface, and efficient heating from both sides are performed. The temperature gradually decreases, and the heat generated by the heater is limited only to the initial stage. In addition to the effect of the penetration of far-infrared rays into the inside of the food, thawing with less temperature unevenness between the center and the surface becomes possible.

(2) During thawing, cold air is allowed to flow down and flow into the food from the upper part of the room, so that the surface of the food is cooled evenly and the temperature rise is further suppressed, thereby preventing deterioration of the food.

(3) The weight, component, and shape of the food are indirectly detected based on the difference in the temperature rise gradient of the temperature sensor, and fuzzy inference is performed based on a combination of the thickness setting input. The optimal second stage time magnification is determined accordingly, and the optimal heating time is automatically set to advance thawing, so that a good thawing finish can be obtained even if the weight, type, and thickness of the food changes. Can be

(4) In the initial stage of defrosting, both the radiation heater and the heating heater are energized to perform rapid heating from the top and bottom, so that defrosting can be performed in a short time while maintaining quality.

(5) After the thawing is completed, the thawing room is kept cool in a temperature zone between the freezing room temperature and the refrigerator room temperature (for example, a partial freezing temperature of -3 ° C.). The freshness is maintained in an environment suitable for preservation of living things such as fish meat even if it is left as it is without rising, the food can be used at any time, and the usability is extremely good.

[Brief description of the drawings]

FIG. 1 is a perspective view of a thawing chamber showing one embodiment of the present invention.

FIG. 2 is a sectional view of the thawing chamber of FIG. 1 taken along the line AA '.

FIG. 3 is a longitudinal sectional view of a refrigerator with a thawing room having the thawing room of FIG. 1;

FIG. 4 is an enlarged view of a thawing operation plate.

FIG. 5 is a control block diagram.

FIG. 6 is a flowchart of defrosting control.

FIG. 7 is a table diagram of a fuzzy rule.

FIG. 8 is a time chart during thawing and a temperature characteristic diagram of the food to be thawed.

FIG. 9 is a perspective view of a thawing box showing a conventional example.

10 is a sectional view of the thawing box of FIG. 10 taken along the line BB '.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Cooling room 14 Defrosting room 17 Blower 29 Radiant heater 31 Heater 32 Temperature sensor 43 Thickness setting switch 44 Defrosting switch 45 Control means 46 First stage time timer 54 Fuzzy inference means 56 Memory device

Continuation of the front page (56) References JP-A-64-57079 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F25D 23/12

Claims (1)

(57) [Claims] 1. A reflector having a curved anti-sloping surface, a bottom plate disposed opposite to the reflector, and a substantially U-shaped side plate connected to the reflector and the bottom plate at an outer peripheral portion. A metal inner box formed in a box shape by the reflection plate, the bottom plate, and the side plate; a door provided at the front opening of the inner box so as to be openable and closable; and a synthetic resin outer box covering the inner box. A heat insulating material inserted between the inner box and the outer box, a discharge air path and a suction air path, and a radiation heater provided at a predetermined interval below the reflector.
A heater that is thermally conductively attached to the back surface of the bottom plate, a temperature sensor that is thermally conductively attached to substantially the center of the back surface of the bottom plate, and A thaw plate that is conductively and detachably installed, a discharge port formed in the reflection plate and communicating with the discharge air passage and the inside of the inner box, and a suction passage formed in the side plate and the inside of the inner box. A thawing chamber provided with a suction port to communicate with, a cooling chamber provided with the thawing chamber in one section, a blower for forcibly blowing cool air cooled by a cooler of a refrigeration cycle to the cooling chamber and the thawing chamber; A damper thermo that is provided at the entrance to the discharge air passage of the room and adjusts the amount of inflow of cold air, a thawing switch that performs thawing action, and a thickness setting switch that inputs the thickness of the food to be thawed,
During thawing, the damper thermostat is forcibly opened, the blower is forcibly operated, and the thawing time is divided into a plurality of stages. The time from the start of thawing until the temperature of the temperature sensor rises to a predetermined temperature is defined as a first stage. The radiant heater and the heater are both energized, and in the subsequent steps, the energization of the heater is stopped, and the energization of the radiant heater is controlled by a setting input of the thickness setting switch and the temperature of the temperature sensor is set to a predetermined value. A memory device for storing a control rule based on an empirical rule for obtaining an optimal time of the second stage after the temperature rises, and a time until the temperature sensor rises to a predetermined temperature and the memory device is taken out of the memory device. based on the control rule was performs fuzzy logic operations, provided with a fuzzy inference means for calculating the time of the second stage, each stage energization rate And intermittent energization to lower each time elapses, and the non-decompression during the third more composed decompression chamber refrigerator with control means formed by maintaining the temperature zone between the refrigeration temperature the decompression chamber and refrigerated temperatures.